Chad M. Shade

Zinc-Adeninate Metal−Organic Framework for Aqueous Encapsulation and Sensitization of Near-infrared and Visible Emitting Lanthanide Cations

Luminescent metal-organic frameworks (MOFs), Ln(3+)@bio-MOF-1, were synthesized via postsynthetic cation exchange of bio-MOF-1 with Tb(3+), Sm(3+), Eu(3+), or Yb(3+), and their photophysical properties were studied. We demonstrate that bio-MOF-1 encapsulates and sensitizes visible and near-infrared emitting lanthanide cations in aqueous solution.

Pyridine-based lanthanide complexes combining MRI and NIR luminescence activities.

A series of novel triazole derivative pyridine-based polyamino-polycarboxylate ligands has been synthesized for lanthanide complexation. This versatile platform of chelating agents combines advantageous properties for both magnetic resonance (MR) and optical imaging applications of the corresponding Gd(3+) and near-infrared luminescent lanthanide complexes. The thermodynamic stability constants of the Ln(3+) complexes, as assessed by pH potentiometric measurements, are in the range log K(LnL)=17-19, with a high selectivity for lanthanides over Ca(2+), Cu(2+), and Zn(2+). The complexes are bishydrated, an important advantage to obtain high relaxivities for the Gd(3+) chelates. The water exchange of the Gd(3+) complexes (k(ex)(298)=7.7-9.3×10(6) s(-1)) is faster than that of clinically used magnetic resonance imaging (MRI) contrast agents and proceeds through a dissociatively activated mechanism, as evidenced by the positive activation volumes (ΔV(≠)=7.2-8.8 cm(3) mol(-1)). The new triazole ligands allow a considerable shift towards lower excitation energies of the luminescent lanthanide complexes as compared to the parent pyridinic complex, which is a significant advantage in the perspective of biological applications. In addition, they provide increased epsilon values resulting in a larger number of emitted photons and better detection sensitivity. The most conjugated system PheTPy, bearing a phenyl-triazole pendant on the pyridine ring, is particularly promising as it displays the lowest excitation and triplet-state energies associated with good quantum yields for both Nd(3+) and Yb(3+) complexes. Cellular and in vivo toxicity studies in mice evidenced the non-toxicity and the safe use of such bishydrated complexes in animal experiments. Overall, these pyridinic ligands constitute a highly versatile platform for the simultaneous optimization of both MRI and optical properties of the Gd(3+) and the luminescent lanthanide complexes, respectively.

Lanthanide sensitization in II-VI semiconductor materials: a case study with terbium(III) and europium(III) in zinc sulfide nanoparticles.

This work explores the sensitization of luminescent lanthanide Tb(3+) and Eu(3+) cations by the electronic structure of zinc sulfide (ZnS) semiconductor nanoparticles. Excitation spectra collected while monitoring the lanthanide emission bands reveal that the ZnS nanoparticles act as an antenna for the sensitization of Tb(3+) and Eu(3+). The mechanism of lanthanide ion luminescence sensitization is rationalized in terms of an energy and charge transfer between trap sites and is based on a semiempirical model, proposed by Dorenbos and co-workers (Dorenbos, P. J. Phys.: Condens. Matter 2003, 15, 8417-8434; J. Lumin. 2004, 108, 301-305; J. Lumin. 2005, 111, 89-104. Dorenbos, P.; van der Kolk, E. Appl. Phys. Lett. 2006, 89, 061122-1-061122-3; Opt. Mater. 2008, 30, 1052-1057. Dorenbos, P. J. Alloys Compd. 2009, 488, 568-573; references 1-6.) to describe the energy level scheme. This model implies that the mechanisms of luminescence sensitization of Tb(3+) and Eu(3+) in ZnS nanoparticles are different; namely, Tb(3+) acts as a hole trap, whereas Eu(3+) acts as an electron trap. Further testing of this model is made by extending the studies from ZnS nanoparticles to other II-VI semiconductor materials; namely, CdSe, CdS, and ZnSe.

Decorated carbon nanotubes with unique oxygen sensitivity

The relatively simple and robust architecture of microelectronic devices based on carbon nanotubes, in conjunction with their environmental sensitivity, places them among the leading candidates for incorporation into ultraportable or wearable chemical analysis platforms. We used single-walled carbon nanotube (SWNT) networks to establish a mechanistic understanding of the solid-state oxygen sensitivity of a Eu(3+)-containing dendrimer complex. After illumination with 365 nm light, the SWNT networks decorated with the Eu(3+) dendrimer show bimodal (optical spectroscopic and electrical conductance) sensitivity towards oxygen gas at room temperature under ambient pressure. We investigated the mechanism of this unique oxygen sensitivity with time-resolved and steady-state optical spectroscopy, analysis of excited-state luminescence lifetimes and solid-state electrical transport measurements. We demonstrate a potential application of this system by showing a reversible and linear electrical response to oxygen gas in the tested range (5-27%).

Luminescence targeting and imaging using a nanoscale generation 3 dendrimer in an in vivo colorectal metastatic rat model

UNLABELLED Surgery is currently the best approach for treating either primary or metastatic hepatic malignancies. Because only 20% of hepatic cancers are operable in patients, several types of regional therapy (RT) are emerging as alternate treatment modalities. However, RTs can have their own limitations at controlling tumor growth or may lack the ability to detect such metastases. Additional strategies can be implemented to enhance their efficacy. An animal model of hepatic metastases coupled with a gastroduodenal artery (GDA) cannulation technique may provide a site to apply such therapies. In our study, splenic injections were performed with CC531 adenocarcinoma cells, which generated metastatic hepatic tumors in WAG/RijHsd rats. Cannulation of GDA was achieved via a polyethylene catheter. Infusion of generation 3 polyamidoamine 4-amino-1,8-naphthalimide dendrimer containing 8 europium ions (Eu-G3P4A18N) via the GDA resulted in luminescence of the hepatic metastatic nodules. Imaging of the metastatic hepatic nodules was obtained with the help of a cooled charge coupled device (CCD) camera. FROM THE CLINICAL EDITOR Hepatic malignancies represent a major therapeutic challenge, despite the available surgical and oncologic treatment modalities. In this paper, an animal model of hepatic adenocarcinoma is used in demonstrating successful targeting of spleen metastases with generation 3 polyamidoamine 4-amino-1,8-naphthalimide dendrimer containing 8 europium ions (Eu-G3P4A18N) for luminescence imaging.

Hydrophobic chromophore cargo in micellar structures: a different strategy to sensitize lanthanide cations

We propose a new approach for the versatile sensitization of luminescent lanthanide cations. A hydrophobic chromophore is incorporated into a micellar assembly formed by the amphiphilic lanthanide chelate. The sensitizer to lanthanide energy transfer occurs between the two moieties without covalent linkage.